Oxidative halogenation and optional dehydrogenation of c3+hydrocarbons

ABSTRACT

An oxidative halogenation and optional dehydrogenation process involving contacting a reactant hydrocarbon having three or more carbon atoms, such as propane or propene, or a halogenated derivative thereof, with a source of halogen, and optionally, a source of oxygen in the presence of a rare earth halide or rare earth oxyhalide catalyst, so as to form a halogenated hydrocarbon product, such as allyl chloride, having three or more carbon atoms and having a greater number of halogen substituents as compared with the reactant hydrocarbon, and optionally, an olefinic co-product, such as propene. The less desired of the two products, that is, the halogenated hydrocarbon or the olefin as the case may be, can be recycled to the process to maximize the production of the desired product.

Cross-Reference to Related Applications: This application is a 371 ofInternational Patent Application no. PCT/US 02/13011, filed Apr. 23,2002, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 60/293,123, filed May 23, 2001.

This invention pertains to a process for the oxidative halogenation andoptional dehydrogenation of a reactant hydrocarbon having three or morecarbon atoms (hereinafter referred to as a “C3+ hydrocarbon”). For thepurposes of this discussion, the term “oxidative halogenation andoptional dehydrogenation” shall refer to a process wherein a reactanthydrocarbon having three or more carbon atoms, or a halogenatedderivative thereof, is contacted with a source of halogen and,optionally, a source of oxygen so as to form a halogenated hydrocarbonproduct having three or more carbon atoms and having a greater number ofhalogen substituents as compared with the reactant hydrocarbon, andoptionally, an olefinic hydrocarbon product having three or more carbonatoms.

Olefinic C3+ hydrocarbons and halogenated C3+ hydrocarbons, for example,propene, chloropropanes, and chloropropenes, more preferably, propene,dichloropropane, and ally chloride, find utility in a broad spectrum ofapplications. Propene (or propylene) is an important olefin feedstockfor many useful products, such as polypropylene, isopropyl alcohol, andcumene. Dichloropropane is useful in fumigants and solvent mixtures.Allyl chloride is a precursor to allyl alcohol and epichlorohydrin.

While there are several known methods for preparing propene by thedehydrogenation of propane, none are practiced on a commercial scale,because the methods are too energy and capital intensive. Propene isproduced mainly as a co-product in two major petrochemical processes:steam cracking, from which the major products are ethylene, propene,butenes and butadiene, and catalytic cracking, from which the majorproducts are naphtha (gasoline), propene, and butenes. Both of theseprocesses provide essentially all of the propene that the market hasneeded up to this time. As propene demand increases more rapidly thanthe market for ethylene and/or gasoline, it would be useful to have aroute to propene that is not tied to these other products.

The uncatalyzed oxidative halogenation of olefinic hydrocarbons havingthree or more carbon atoms, such as propene, with chlorine to thecorresponding unsaturated halogenated hydrocarbons, such aschloropropenes, referred to as the “hot chlorination route,” isdescribed in the following representative art of K. Weissermel and H.-J.Arpe, “Industrial Organic Chemistry”, 2^(nd) edition, VCHVerlagsgesellschaft mbH, Weinheim, pp. 291–293. The process, whileefficient, is disadvantageously conducted at high temperatures.

The reactions of halogens with saturated C3+ hydrocarbons byboth-talyzed and catalytic routes have also been reported in the art;see for example, Olah and Molnar “Hydrocarbon Chemistry,” John Wiley &Sons, 1995, pp. 415–432, and Wittcoff and Reuben “Industrial OrganicChemicals,” John Wiley & Sons, 1996, pp. 338–341. Catalyzed routes arealso reported by Weissermel and Arpe, Ibid, p. 292. The catalyzed routesare not practiced commercially, because the “hot chlorination” route ismore efficient and cost effective. In the catalyzed process, however,the reactant hydrocarbon is contacted under reaction conditions with asource of halogen and, optionally, a source of oxygen in the presence ofan oxidative halogenation catalyst. Typically, the catalyst contains acopper compound, an iron compound, or cerium oxide, optionally, with oneor more alkali or alkaline earth metal chlorides, and/or optionally,with one or more rare earth compounds, supported on an inert carrier,typically alumina, silica, or an aluminosilicate.

Disadvantageously, the catalyzed processes of the prior art produce anunacceptable quantity of highly halogenated products, includingperhalogenated products, which are less desirable than themonohalogenated and dihalogenated products. As a further disadvantage,the prior art processes produce an unacceptable quantity of deepoxidation products (CO_(x)), specifically, carbon monoxide and carbondioxide. The production of lower value highly halogenated products andundesirable oxidized products irretrievably wastes the hydrocarbon feedand creates product separation and by-product disposal problems. As afurther disadvantage, many of the transition metal halides used ascatalysts for this type of process exhibit significant vapor pressure atreaction temperatures; that is, these catalysts are volatile. Thevolatility generally produces a decline in catalyst activity and/ordeposition of corrosive materials in downstream parts of the processequipment.

As evidenced from the above, the catalyzed oxidative halogenation ofhydrocarbons having three or more carbon atoms is substantiallynon-selective for the corresponding mono- and di-halogenated hydrocarbonproducts. Accordingly, an increase in selectivity to mono- anddi-halogenated hydrocarbons is needed. Likewise, a reduction inselectivities to higher halogenated products, including perhalogenatedproducts, and oxygenated products is needed. Also, increases in catalystactivity and catalyst lifetime are needed. With these improvements, theoxidative halogenation of C3+ hydrocarbons to halogenated C3+hydrocarbons, preferably, mono- and di-halogenated C3+ hydrocarbons,such as dichloropropane and allyl chloride, and optionally, tounsaturated hydrocabon products, preferably olefins, should be moreattractive.

This invention provides for a novel oxidative halogenation and optionaldehydrogenation process of preparing a halogenated C3+ hydrocarbon, andoptionally, a C3+ olefinic hydrocarbon. The novel process of thisinvention comprises contacting a reactant hydrocarbon having three ormore carbon atoms (a C3+ hydrocarbon), or a halogenated derivativethereof, with a source of halogen and, optionally, a source of oxygen inthe presence of a catalyst under process conditions sufficient toprepare a halogenated hydrocarbon product having three or more carbonatoms (a halogenated C3+ hydrocarbon) and having a greater number ofhalogen substituents as compared with the reactant hydrocarbon.Optionally, a second product is produced comprising an olefinichydrocarbon having three or more carbon atoms. In this process, it ispreferred to employ the source of oxygen. The catalyst employed in thisprocess comprises a rare earth halide or rare earth oxyhalide compoundsubstantially free of copper and iron, with the proviso that when ceriumis present in the catalyst, at least one other rare earth element isalso present in the catalyst.

The novel oxidative halogenation and optional dehydrogenation process ofthis invention advantageously converts a reactant hydrocarbon havingthree or more carbon atoms, or a halogenated derivative thereof, in thepresence of a source of halogen and, preferably, a source of oxygen intoa halogenated hydrocarbon product having three or more carbon atoms andhaving an increased number of halogen substituents as compared with thereactant hydrocarbon. Optionally, a second hydrocarbon product may beconcurrently produced comprising a C3+ olefinic hydrocarbon. In apreferred embodiment, the process of this invention can be beneficiallyemployed to oxidatively chlorinate propane in the presence of hydrogenchloride and oxygen to allyl chloride and propylene. As compared withprior art processes, the process of this invention advantageouslyproduces halogenated hydrocarbon product, preferably, mono- anddi-halogenated hydrocarbon products and, optionally, olefinichydrocarbon product in high selectivities with essentially noperhalogenated halocarbon by-products and low levels, if any, ofundesirable oxygenates, such as, carbon monoxide and carbon dioxide. Thelower selectivity to perhalogenated halocarbons and undesirableoxygenated by-products correlates with a more efficient use of reactanthydrocarbon, a higher productivity of the desired lower halogenatedhydrocarbon products and optional olefin, and fewer separation and wastedisposal problems. As an additional advantage, the less desired productformed, either olefin or halogenated product as the case may be, may berecycled to the oxidative halogenation process to maximize theproduction of the more desired product.

In addition to the above advantages, the catalyst employed in theprocess of this invention does not require a conventional carrier orsupport, such as alumina or silica. Instead, the catalyst employed inthis invention beneficially comprises a rare earth halide or rare earthoxyhalide compound that uniquely functions both as a catalyst supportand as a source of a further catalytically active rare earth componentUnlike many heterogeneous catalysts of the prior art, the rare earthhalide catalyst of this invention is beneficially soluble in water.Accordingly, should process equipment, such as filters, valves,circulating tubes, and small or intricate parts of reactors, becomeplugged with particles of the rare earth halide catalyst, then a simplewater wash can advantageously dissolve the plugged particles and restorethe equipment to working order. As a further advantage, the catalystsused in the process of this invention are significantly less volatile,as compared with the prior art catalysts. Accordingly, the rare earthhalide and rare earth oxyhalide catalysts employed in the process ofthis invention possess an acceptable reaction rate and a long lifetime,and further, present essentially no downstream contamination orcorrosion problems.

All of the aforementioned properties render the process of thisinvention uniquely attractive for converting a reactant C3+ hydrocarbon,or a halogenated derivative thereof, into a halogenated C3+ hydrocarbonhaving a greater number of halogen substituents than in the reactanthydrocarbon, and optionally, into a co-product C3+ olefinic hydrocarbon.In preferred embodiments of this invention, mono- and/or di-halogenatedhydrocarbon products are selectively produced along with the olefin. Asa most preferred advantage, the process of this invention canoxidatively dehydrogenate and halogenate propane selectivity to propeneand monohalogenated propene, preferably, allyl chloride or allylbromide.

In the novel oxidative halogenation and optional dehydrogenation processof this invention, a halogenated hydrocarbon product having three ormore carbon atoms, preferably a mono- and/or di-halogenated hydrocarbonproduct having three or more carbon atoms, and an optional olefinicco-product are selectively produced with essentially no formation ofperhalogenated chlorocarbon product and with advantageously low levelsof undesirable oxygenated by-products, such as, CO_(x) oxygenates (COand CO₂). The novel process of this invention comprises contacting ahydrocarbon having three or more carbon atoms (a C3+ hydrocarbon), or ahalogenated derivative thereof, with a source of halogen and,optionally, a source of oxygen in the presence of a catalyst underprocess conditions sufficient to prepare a halogenated hydrocarbonproduct having three or more carbon atoms (a halogenated C3+hydrocarbon) and having a greater number of halogen substituents ascompared with the reactant hydrocarbon. Optionally, a co-productcomprising an olefin having three or more carbon atoms is formed in theprocess. In a preferred embodiment of the invention, the source ofoxygen is employed. The unique catalyst employed in the oxidativehalogenation and optional dehydrogenation process of this inventioncomprises a rare earth halide or rare earth oxyhalide compound that issubstantially free of copper and iron, with the further proviso thatwhen cerium is present in the catalyst, at least one other rare earthelement is also present in the catalyst.

The term “oxidative halogenation and optional dehydrogenation” shall insome occurrences hereinafter be simply referred to “oxidativehalogenation.” This shortened term is used for convenience only andshall not limit the process in any fashion. The process of thisinvention shall include both halogenation reactions wherein halogenatedproducts are formed as well as dehydrogenation reactions wherein lesssaturated hydrocarbon products (for example, olefins) are formed, ascompared with the reactant hydrocarbons (for example, alkanes).

In a preferred embodiment of this invention, the process produces as aco-product a C3+ olefin, preferably, propylene. The co-product olefincan be advantageously recycled to the oxidative halogenation process forfurther processing to halogenated hydrocarbons, preferably, allylchloride.

In another preferred embodiment of this invention, the halogenatedhydrocarbon product, such as allyl chloride, can be recycled to theoxidative halogenation process for further processing to olefinicproducts, such as propylene.

In a more preferred embodiment of this invention, the process comprisescontacting propane with a source of halogen and, optionally, a source ofoxygen in the presence of a catalyst under process conditions sufficientto prepare allyl halide and propylene, the catalyst comprising a rareearth halide or rare earth oxyhalide that is substantially free ofcopper and iron, with the further proviso that when cerium is present inthe catalyst, at least one other rare earth element is also present inthe catalyst. In a most preferred embodiment, the source of halogen ishydrogen chloride; the halogenated C3+ hydrocarbon produced is allylchloride; and the co-product olefin produced is propylene.

With respect to the catalyst, in a preferred embodiment, the rare earthhalide or rare earth oxyhalide catalyst is “porous,” which, for thepurposes of this invention, means that the catalyst has a surface areaof least 5 m²/g, as determined by the BET (Brunauer-Emmet-Teller) methodof measuring surface area, described by S. Brunauer, P. H. Emmett, andE. Teller, Journal of the American Chemical Society, 60, 309 (1938). Inanother more preferred embodiment of this invention, the rare earthhalide is lanthanum chloride, and the rare earth oxyhalide is lanthanumoxychloride.

The reactant hydrocarbon used in the oxidative halogenation process ofthis invention comprises a hydrocarbon having three or more carbon atomsor a halogenated hydrocarbon having three or more carbon atoms, eitherbeing capable of acquiring more halogen substituents in accordance withthe process described herein. The halogen substituent of the halogenatedreactant hydrocarbon is preferably selected from chlorine, bromine,iodine, and mixtures thereof, more preferably, chlorine and bromine.One, two, or three halogen substituents may be present on thehalogenated hydrocarbon; but for the purposes of this invention thereactant halogenated hydrocarbon is not a perhalogenated compound, as inhexachloropropane. Different halogen substituents may be suitablypresent in the halogenated hydrocarbon reactant, as illustrated bybromochloropropane and the like. Suitable examples of reactanthydrocarbons and reactant halogenated hydrocarbons include, withoutlimitation, alkanes and alkenes, and halogenated derivatives thereof,including propane, butane, pentane, chloropropane, chlorobutane,dichloropropane, dichlorobutane, bromopropane, bromobutane,dibromopropane, dibromobutane, bromochloropropane, and the like,including higher homologues thereof. Likewise, cyclic aliphatichydrocarbons, such as cyclohexane, and aromatic hydrocarbons, such asbenzene, ethylbenzene, and cumene, including alkyl and halo substitutedcyclic aliphatics and aromatics, may be employed. Preferably, thereactant hydrocarbon or reactant halogenated hydrocarbon is a C₃₋₂₀hydrocarbon, more preferably, a C₃₋₁₀ hydrocarbon. The most preferredreactant hydrocarbon is selected from propane and propene. The reactanthydrocarbon may be provided to the oxidative halogenation process as apure feed stream, or diluted with an inert diluent as describedhereinafter, or as a mixture of reactant hydrocarbons, optionally,further in combination with an inert diluent.

The source of halogen, which is employed in the process of thisinvention, may be any inorganic or organic halogen-containing compoundthat is capable of transferring its halogen atom(s) to the reactanthydrocarbon. Suitable non-limiting examples of the source of halogeninclude chlorine, bromine, iodine, hydrogen chloride, hydrogen bromide,hydrogen iodide, and halogenated hydrocarbons having one or more labilehalogen substituents (that is, transferable halogen substituents).Examples of the latter include perhalocarbons, such as carbontetrachloride and carbon tetrabromide, as well as highly halogenatedhydrocarbons having, for example, three or more halogen atoms.Non-limiting examples of highly halogenated hydrocarbons having three ormore halogen substituents, at least one substituent of which is labile,include chloroform and tribromomethane. Preferably, the source ofhalogen is a source of chlorine or a source of bromine, more preferably,hydrogen chloride or hydrogen bromide, most preferably, hydrogenchloride.

The source of halogen may be provided to the process in any amount thatis effective in producing the desired halogenated hydrocarbon product.Typically, the amount of halogen source will vary depending upon thespecific process stoichiometry, the reactor design, and safetyconsiderations. It is possible, for example, to use a stoichiometricamount of halogen source with respect to the reactant hydrocarbon orwith respect to oxygen, if oxygen is present. Alternatively, the sourceof halogen may be used in an amount that is greater or less than thestoichiometric amount, if desired. In one embodiment illustrative of theinvention, propane can be oxidatively chlorinated with chlorine to formchloropropane and hydrogen chloride, the stoichiometric reaction ofwhich is shown in Equation (I) hereinafter:CH₃CH₂CH₃+Cl₂→CH₃CHClCH₃+HCl   (I)The aforementioned process, which does not employ oxygen, would usuallybe conducted at a stoichiometric molar ratio of chlorine to propane orat a higher than stoichiometric molar ratio of chlorine to propane(molar ratio ≧1 Cl₂:1 CH₃CH₂CH₃), and preferably, would be conducted inan excess of chlorine to ensure complete conversion of propane. In thisembodiment of the invention, the molar ratio of source of halogen toreactant hydrocarbon is generally greater than 1/1, preferably, greaterthan 2/1, and more preferably, greater than 4/1. Generally, in thisembodiment of the invention the molar ratio of source of halogen toreactant hydrocarbon is less than 20/1, preferably, less than 15/1, andmore preferably, less than 10/1.

In another embodiment illustrative of the invention, propane can beoxidatively chlorinated and dehydrogenated with hydrogen chloride in thepresence of oxygen to produce allyl chloride, propylene, and water, thestoichiometric reaction of which is shown hereinafter in Equation (II):2 CH₃CH₂CH₃+HCl+1.5 O₂→CH₂═CHCH₃+CH₂═CHCH₂Cl+3H₂O   (II)This embodiment of the process, which employs oxygen, is usuallyconducted “fuel-rich,” due to safety considerations. The term“fuel-rich” means that oxygen is the limiting reagent and a molar excessof reactant hydrocarbon is used relative to oxygen. Typically, forexample, the molar ratio of hydrocarbon to oxygen is chosen foroperation outside the fuel-rich flammability limit of the mixture,although this is not absolutely required. In addition, a stoichiometricmolar ratio of hydrogen halide to oxygen (for example, 1 HCl:1.5 O₂) istypically employed to ensure complete reaction of both the source ofhalogen and oxygen.

A source of oxygen is not required for the process of this invention;however, use of a source of oxygen is preferred, particularly when thesource of halogen contains hydrogen atoms. The source of oxygen can beany oxygen-containing gas, such as, commercially pure molecular oxygen,air, oxygen-enriched air, or a mixture of oxygen with a diluent gas thatdoes not interfere with the oxidative halogenation process, such as,nitrogen, argon, helium, carbon monoxide, carbon dioxide, methane, andmixtures thereof. As noted above, when oxygen is employed, the feed tothe oxidative halogenation reactor is generally fuel-rich. Typically,the molar ratio of reactant hydrocarbon to oxygen is greater than 2/1,preferably, greater than 4/1, and more preferably, greater than 5/1.Typically, the molar ratio of reactant hydrocarbon to oxygen is lessthan 20/1, preferably, less than 15/1, and more preferably, less than10/1.

Based on the description hereinabove, one skilled in the art will knowhow to determine the molar quantities of reactant C3+ hydrocarbon,source of halogen, and source of oxygen suitable for reactantcombinations different from those illustrated herein.

Optionally, if desired, the feed, comprising reactant hydrocarbon,source of halogen, and optional source of oxygen, can be diluted with adiluent or carrier gas, which may be any essentially non-reactive gasthat does not substantially interfere with the oxidative halogenationprocess. The diluent may assist in removing products and heat from thereactor and in reducing the number of undesirable side-reactions.Non-limiting examples of suitable diluents include nitrogen, argon,helium, carbon monoxide, carbon dioxide, methane, and mixtures thereof.The quantity of diluent employed is typically greater than 10 molepercent, and preferably, greater than 20 mole percent, based on thetotal moles of feed to the reactor, that is, total moles of reactanthydrocarbon, source of halogen, source of oxygen, and diluent. Thequantity of diluent employed is typically less than 90 mole percent, andpreferably, less than 70 mole percent, based on the total moles of feedto the reactor.

The catalyst employed in the oxidative halogenation process of thisinvention comprises, in one aspect, a rare earth halide compound. Therare earths are a group of 17 elements consisting of scandium (atomicnumber 21), yttrium (atomic number 39) and the lanthanides (atomicnumbers 57–71) [James B. Hedrick, U.S. Geological Survey—MineralsInformation—1997, “Rare-Earth Metals”]. Preferably, herein, the term istaken to mean an element selected from lanthanum, cerium, neodymium,praseodymium, dysprosium, samarium, yttrium, gadolinium, erbium,ytterbium, holmium, terbium, europium, thulium, lutetium, and mixturesthereof Preferred rare earth elements for use in the aforementionedoxidative halogenation process are those that are typically consideredas being single valency metals. The catalytic performance of rare earthhalides using multi-valency metals appears to be less desirable thanrare earth halides using single valency metals. The rare earth elementfor this invention is preferably selected from lanthanum,praeseodyrnium, neodymium, and mixtures thereof. Most preferably, therare earth element used in the catalyst is lanthanum or a mixture oflanthanum with other rare earth elements.

Preferably, the rare earth halide is represented by the formula MX₃wherein M is at least one rare earth element selected from the groupconsisting of lanthanum, cerium, neodymium, praseodymium, dysprosium,samarium, yttrium, gadolinium, erbium, ytterbium, holmium, terbium,europium, thulium, lutetium, and mixtures thereof; and wherein each X isindependently selected from chloride, bromide, and iodide. Morepreferably, X is chloride, and the more preferred rare earth halide isrepresented by the formula MCl₃, wherein M is defined hereinbefore. Mostpreferably, X is chloride and M is lanthanum or a mixture of lanthanumwith other rare earth elements.

In a preferred embodiment, the rare earth halide is porous, meaning thattypically the rare earth halide has a BET surface area of greater than 5m²/g. Preferably, the BET surface area is greater than about 10 m²/g,more preferably, greater than about 15 m²/g, even more preferably,greater than about 20 m²/g, and most preferably, greater than about 30m²/g. For these above measurements, a nitrogen adsorption isotherm wasmeasured at 77K and the surface area was calculated from the isothermdata utilizing the BET method, as referenced earlier herein.

In another aspect, the catalyst employed in this invention comprises arare earth oxyhalide, the rare earths being the seventeen elementsidentified hereinabove. Preferably, the rare earth oxyhalide isrepresented by the formula MOX, wherein M is at least one rare earthelement selected from the group consisting of lanthanum, cerium,neodymium, praseodymium, dysprosium, samarium, yttrium, gadolinium,erbium, ytterbium, holmium, terbium, europium, thulium, lutetium, andmixtures thereof; and wherein each X is independently selected from thegroup consisting of chloride, bromide, and iodide. More preferably, therare earth halide is a rare earth oxychloride, represented by theformula MOCl, wherein M is defined hereinbefore. Most preferably, X ischloride, and M is lanthanum or a mixture of lanthanum with other rareearth elements.

In a preferred embodiment, the rare earth oxyhalide is also porous,which generally implies a BET surface area of greater than about 12m²/g. Preferably, the rare earth oxyhalide has a BET surface area ofgreater than about 15 m²/g, more preferably, greater than about 20 m²/g,and most preferably, greater than about 30 m²/g. Generally, the BETsurface area of the rare earth oxyhalide is less than about 200 m²/g. Inaddition, it is noted that the MOCl phases possess characteristic powderX-Ray Diffraction (XRD) patterns that are distinct from the MCl₃ phases.

In general, the presence in the catalyst of metals that are capable ofoxidation-reduction (redox) is undesirable. Redox metals typicallyinclude transition metals that have more than one stable oxidationstate, such as iron, copper, and manganese. The rare earth halide oroxyhalide catalyst of this invention is specifically required to besubstantially free of copper and iron. The term “substantially free”means that the atom ratio of rare earth element to redox metal,preferably iron or copper, is greater than about 1/1, preferably greaterthan about 10/1, more preferably greater than about 15/1, and mostpreferably greater than about 50/1. In addition, cerium, a lanthaniderare earth element, is known to be an oxidation-reduction catalysthaving the ability to access both the 3⁺ and 4⁺ oxidation states. Forthis reason, if the rare earth metal is cerium, the catalyst of thisinvention further comprises at least one more rare earth metal otherthan cerium. Preferably, if one of the rare earth metals is cerium, thecerium is provided in a molar ratio that is less than the total amountof other rare earth metals present in the catalyst. More preferably,however, substantially no cerium is present in the catalyst. By“substantially no cerium” it is meant that any cerium present is in anamount less than about 10 atom percent, preferably, less than about 5atom percent, and even more preferably, less than about 1 atom percentof the total rare earth components.

In an alternative embodiment of this invention, the rare earth halide orrare earth oxyhalide catalyst, described hereinbefore, may be bound to,extruded with, or deposited onto a conventional catalyst support, suchas alumina, silica, silica-alumina, porous aluminosilicate (zeolite),silica-magnesia, bauxite, magnesia, silicon carbide, titanium oxide,zirconium oxide, zirconium silicate, or any combination thereof. In thisembodiment, the conventional support is used in a quantity greater thanabout 1 weight percent, but less than about 90 weight percent,preferably, less than about 70 weight percent, more preferably, lessthan about 50 weight percent, based on the total weight of the catalystand catalyst support.

It may also be advantageous to include other elements within thecatalyst. For example, preferable elemental additives include alkali andalkaline earths, boron, phosphorous, sulfur, germanium, titanium,zirconium, hafnium, and combinations thereof. These elements can bepresent to alter the catalytic performance of the composition or toimprove the mechanical properties (for example attrition-resistance) ofthe material. In a preferred embodiment, the elemental additive iscalcium. In another preferred embodiment, the elemental additive is notaluminum or silicon. The total concentration of elemental additives inthe catalyst is typically greater than about 0.01 weight percent andtypically less than about 20 weight percent, based on the total weightof the catalyst.

The rare earth halide and rare earth oxyhalide compounds may be obtainedcommercially or prepared by methods published in the art. A methodcurrently felt to be preferable for forming the porous rare earthoxyhalide (MOX) comprises the following steps: (a) preparing a solutionof a halide salt of the rare earth element or elements in a solventcomprising either water, an alcohol, or mixtures thereof; (b) adding abase to cause the formation of a precipitate; and (c) collecting andcalcining the precipitate in order to form the MOX. Preferably, thehalide salt is a rare earth chloride salt, for example, any commerciallyavailable rare earth chloride. Typically, the base is anitrogen-containing base selected from ammonium hydroxide, alkyl amines,aryl amines, arylalkyl amines, alkyl ammonium hydroxides, aryl ammoniumhydroxides, arylalkyl ammonium hydroxides, and mixtures thereof. Thenitrogen-containing base may also be provided as a mixture of anitrogen-containing base with other bases that do not contain nitrogen.Preferably, the nitrogen-containing base is ammonium hydroxide ortetra(alkyl)ammonium hydroxide, more preferably, tetra(C₁₋₂₀alkyl)ammonium hydroxide. Porous rare earth oxyhalides may also beproduced by appropriate use of alkali or alkaline earth hydroxides,particularly, with the buffering of a nitrogen-containing base, althoughcaution should be exercised to avoid producing substantially the rareearth hydroxide or oxide. The solvent in Step (a) is preferably water.Generally, the precipitation is conducted at a temperature greater thanabout 0° C. Generally, the precipitation is conducted at a temperatureless than about 200° C., preferably, less than about 100° C. Theprecipitation is conducted generally at about-ambient atmosphericpressure, although higher pressures may be used, as necessary, tomaintain liquid phase at the precipitation temperature employed. Thecalcination is typically conducted at a temperature greater than about200° C., preferably, greater than about 300° C., and less than about800° C., preferably, less than about 600° C. Production of mixedcarboxylic acid and rare earth halide salts also can yield rare earthoxyhalides upon appropriate decomposition.

A method currently felt to be preferable for forming the porous rareearth halide (MX₃) catalyst comprises the following steps: (a) preparinga solution of a halide salt of the rare earth element or elements in asolvent comprising either water, an alcohol, or mixtures thereof; (b)adding a base to cause the formation of a precipitate; (c) collectingand calcining the precipitate; and (d) contacting the calcinedprecipitate with a halogen source. Preferably, the rare earth halide isa rare earth chloride salt, such as any commercially available rareearth chloride. The solvent and base may be any of those mentionedhereinbefore in connection with the formation of MOX. Preferably, thesolvent is water, and the base is a nitrogen-containing base. Theprecipitation is generally conducted at a temperature greater than about0° C. and less than about 200° C., preferably less than about 100° C.,at about ambient atmospheric pressure or a higher pressure so as tomaintain liquid phase. The calcination is typically conducted at atemperature greater than about 200° C., preferably, greater than about300° C., but less than about 800° C., and preferably, less than about600° C. Preferably, the halogen source is a hydrogen halide, such ashydrogen chloride, hydrogen bromide, or hydrogen iodide. Morepreferably, the halogen source is hydrogen chloride. The contacting withthe halogen source is typically conducted at a temperature greater thanabout 100° C. and less than about 500° C. Typical pressures for thecontacting with the source of halogen range from about ambientatmospheric pressure to pressures less than about 150 psia (1,034 kPa).

As noted hereinabove, the rare earth oxyhalide (MOX) compound can beconverted into the rare earth halide (MX₃) compound by treating theoxyhalide with a source of halogen. Since the oxidative halogenationprocess of this invention requires a source of halogen, it is possibleto contact the rare earth oxyhalide with a source of halogen, such aschlorine, in the oxidative halogenation reactor to form the MX₃ catalystin situ.

The oxidative halogenation, and optional dehydrogenation, process ofthis invention can be conducted in a reactor of any conventional designsuitable for gas or liquid phase processes, including batch, fixed bed,fluidized bed, transport bed, continuous and intermittent flow reactors,and catalytic distillation reactors. The process conditions (forexample, molar ratio of feed components, temperature, pressure, weighthourly space velocity), can be varied widely, provided that the desiredhalogenated C3+ hydrocarbon product, preferably mono- or di-halogenatedC3+ hydrocarbon product, and optionally, the desired olefinic product,are obtained. Typically, the process temperature is greater than about100° C., preferably, greater than about 150° C., and more preferably,greater than about 200° C. Typically, the process temperature is lessthan about 600° C., preferably, less than about 500° C., and morepreferably, less than about 450° C. Ordinarily, the process can beconducted at atmospheric pressure; but operation at higher or lowerpressures is possible, as desired. Preferably, the pressure is equal toor greater than about 14 psia (97 kPa), but less than about 150 psia(1,034 kPa). Typically, the total weight hourly space velocity (WHSV) ofthe feed (reactant hydrocarbon, source of halogen, optional source ofoxygen, and optional diluent) is greater than about 0.1 gram total feedper g catalyst per hour (h⁻¹), and preferably, greater than about 1 h⁻¹.Typically, the total weight hourly space velocity of the feed is lessthan about 1,000 h⁻¹, and preferably, less than about 100 h⁻¹.

If the oxidative halogenation and optional dehydrogenation process isconducted as described hereinabove, then a halogenated hydrocarbonproduct is formed that has three or more carbon atoms and a greaternumber of halogen substituents as compared with the reactanthydrocarbon. Halogenated hydrocarbon products beneficially produced bythe process of this invention include halogenated alkanes andhalogenated alkenes, including, without limitation, chloropropane, allylchloride, dichloropropane, bromopropane, dibromopropane, allyl bromide,trichloropropane, tribromopropane, and bromochloropropane. Preferably,the halogenated C3+ hydrocarbon product has C₃₋₂₀ carbon atoms, morepreferably, C₃₋₁₀ carbon atoms. In another preferred embodiment, thehalogenated C3+ hydrocarbon product is a mono- or di-halogenated C3+product. Most preferably, the halogenated hydrocarbon product isdichloropropane or allyl chloride. In another preferred aspect of thisinvention, the halogenated alkene product that is formed is selectivelyhalogenated at a terminal carbon position.

In addition to the halogenated C3+ hydrocarbon product, the process ofthis invention may optionally produce one or more olefins having threeor more carbon atoms, non-limiting examples of which include propene,butenes, and higher homologues thereof. Dienes, as well as monoolefins,may be produced. Preferably, the C3+ olefinic product has C₃₋₂₀ carbonatoms, more preferably, C₃₋₁₀ carbon atoms. More preferably, the C3+olefinic product is propylene.

Typically, in the process of this invention, the number of carbon atomsin the reactant hydrocarbon is essentially conserved in the halogenatedhydrocarbon product and the olefinic product. As the carbon chain in thereactant hydrocarbon is lengthened, however, then the possibilityincreases that some cracking may occur leading to halogenatedhydrocarbon products and olefins of shorter chain length, as comparedwith the reactant hydrocarbon.

In another aspect of this invention, any olefin in the effluent stream,such as propene, may be separated from the halogenated hydrocarbonproducts and recycled to the oxidative halogenation process for furtherprocessing to form halogenated C3+ hydrocarbons, such as, allylchloride. Likewise, any halogenated product, such as allyl chloride, inthe effluent stream may be separated from the olefin products andrecycled to the oxidative halogenation process for further processing toform olefinic product, such as propene. The product to be recycled shalldepend upon the desired end-product that is to be maximized.

For the purposes of the description herein, “conversion” shall bedefined as the mole percentage of reagent that is converted in theoxidative halogenation process of this invention into product(s).Reference may be made to “conversion of reactant C3+ hydrocarbon,” or“conversion of source of halogen,” or “oxygen conversion.” Conversionswill vary depending upon the specific reactant, specific catalyst, andspecific process conditions under consideration. Typically, for theprocess of this invention, the conversion of reactant hydrocarbon isgreater than about 5 mole percent, preferably, greater than about 15mole percent, and more preferably, greater than about 30 mole percent.Typically, for the process of this invention, the conversion of thesource of halogen is greater than about 10 mole percent, preferably,greater than about 25 mole percent, and more preferably, greater thanabout 35 mole percent. Typically, the oxygen conversion is greater thanabout 10 mole percent, preferably, greater than about 20 mole percent,and more preferably, greater than about 40 mole percent.

For the purposes of this invention, “selectivity” shall be defined asthe mole percentage of converted reactant hydrocarbon that is convertedinto a specific product, such as a halogenated hydrocarbon product,olefinic product, or oxygenated by-product, such as CO or CO₂. In theoxidative halogenation process of this invention, the selectivity tohalogenated hydrocarbon product, preferably, dichloropropane or allylchloride, is typically greater than about 15 mole percent, preferably,greater than about 25 mole percent, and more preferably, greater thanabout 30 mole percent. Likewise, the selectivity to olefin is typicallygreater than about 15 mole percent, preferably, greater than about 25mole percent, and more preferably, greater than about 35 mole percent.Advantageously, the oxidative halogenation process of this inventionproduces essentially no perhalogenated products, such as,hexachloropropane, which have lower commercial value. As a furtheradvantage, in preferred embodiments of this invention, low levels ofoxygenated by-products, such as CO_(x) oxygenates (CO and CO₂) areproduced. Typically, the total selectivity to carbon monoxide and carbondioxide is less than about 25 mole percent, preferably, less than about20 mole percent, and more preferably, less than about 15 mole percent.

The following example is provided as an illustration of the process ofthis invention; but the example should not be construed as limiting theinvention in any manner. In light of the disclosure herein, those ofskill in the art will recognize alternative embodiments of the inventionthat fall within the scope of the claims.

EXAMPLE 1

A catalyst composition comprising a porous lanthanum oxychloride wasprepared as follows. Lanthanum chloride (LaCl₃7H₂O, 15 g) was dissolvedin deionized water (100 ml) in a round-bottom flask. Ammonium hydroxide(6 M, 20 ml) was added to the lanthanum chloride solution with stirring.The mixture was centrifuged, and the excess liquid was decanted to yielda gel. In a separate container, calcium lactate (0.247 g, 0.0008 moles)was dissolved to form a saturated solution in deionized water. Thecalcium lactate solution was added with stirring to thelanthanum-containing gel. The gel was dried at 120° C. overnight. Adried solid was recovered, which was calcined under air in an opencontainer at 550° C. for 4 hours to yield a porous lanthanum oxychloridecatalyst (6.84 g). X-ray diffraction of the solid indicated the presenceof a quasi-crystalline form of lanthanum oxychloride. The surface areaof the catalyst was 47 m²/g, as measured by the BET method.

The catalyst prepared hereinabove was crushed to 20×40 US mesh(0.85×0.43 mm) and evaluated in the oxidative chlorination anddehydro-genation of propane as follows. A tubular, nickel alloy reactor,having a ratio of length to diameter of 28.6/1 {6 inches (15.24cm)×0.210 inches (0.533 cm)} was loaded with catalyst (2.02 g). Thereactor was fed a mixture of propane, hydrogen chloride, and oxygen inthe ratios shown in Table 1. The operating temperature was 400° C., andthe operating pressure was atmospheric. The exit gases were analyzed bygas phase chromatography. Results are set forth in Table 1.

TABLE 1 Oxychlorination of Propane Over Lanthanum Catalyst to AllylChloride and Propene¹ Mole Ratio Propane:HCl: WHSV Conv Conv Conv SelSel² Sel² Sel Sel O₂:He h⁻¹ Propane HCl O₂ Propene Allyl Cl 1-ClP CO CO₂1:1:1:7 0.1 51 38 48 40 35 10 5 8 ¹Process Conditions: 400° C.,atmospheric pressure; conversions and selectivities given as molepercentages. ²Allyl Cl = allyl chloride; 1-ClP = 1-chloropropene.From Table 1 it is seen that the lanthanum oxychloride catalyst iscapable of catalyzing the oxidative chlorination and dehydrogenation ofpropane predominantly to allyl chloride and propene. The catalystproduces lesser amounts of deep oxidation products, such as carbonmonoxide and carbon dioxide.

The experimental results presented in Table 1 illustrate the inventionunder the above-disclosed process and analytical conditions. One skilledin the art will recognize that other results may be obtained dependingupon the specific process and analytical conditions employed.

1. A process of oxidative halogenation and optional dehydrogenationcomprising contacting a reactant alkane having three or more carbonatoms, or a halogenated derivative thereof, with a source of halogenand, optionally, a source of oxygen in the presence of a catalyst underprocess conditions sufficient to prepare a halogenated hydrocarbonhaving three or more carbon atoms and having a greater number of halogensubstituents as compared with the reactant alkane and sufficient toprepare an olefin having three or more carbon atoms, the catalystcomprising a rare earth halide or rare earth oxyhalide substantiallyfree of iron and copper such that the atom ratio of the rare earthelement to iron or copper is greater than about 50/1, with the provisothat when cerium is present in the catalyst, then at least one otherrare earth element is also present in the catalyst.
 2. The process ofclaim 1 wherein the reactant alkane is selected from C₃₋₂₀ alkanes. 3.The process of claim 1 wherein the reactant alkane is propane.
 4. Theprocess of claim 1 wherein the source of halogen is selected from thegroup consisting of elemental halogens, hydrogen halides, andhalogenated hydrocarbons having one or more labile halogen substituents.5. The process of claim 4 wherein the source of halogen is elementalchlorine, elemental bromine, or hydrogen chloride.
 6. The process ofclaim 1 wherein the process is conducted at a molar ratio of source ofhalogen to reactant alkane of greater than 1/1 to less than 20/1.
 7. Theprocess of claim 1 wherein the process further comprises oxygen.
 8. Theprocess of claim 7 wherein the source of halogen is provided essentiallyin a stoichiometric amount with respect to the source of oxygen.
 9. Theprocess of claim 7 wherein the source of oxygen is selected from thegroup consisting of molecular oxygen, air, or oxygen-enriched air. 10.The process of claim 7 wherein the process is conducted at a molar ratioof reactant alkane to source of oxygen of greater than 2/1 and less than20/1.
 11. The process of claim 1 wherein the process further comprises adiluent selected from the group consisting of nitrogen, helium, argon,carbon monoxide, carbon dioxide, methane, and mixtures thereof.
 12. Theprocess of claim 11 wherein the diluent is used in an amount that isgreater than 10 mole percent and less than 90 mole percent, based on thetotal moles of reactant alkane and diluent.
 13. The process of claim 1wherein the rare earth halide has a BET surface area greater than 5m²/g.
 14. The process of claim 1 wherein the rare earth halide isrepresented by the formula MX_(3,) wherein M is at least one rare earthelement selected from the group consisting of lanthanum, cerium,neodymium, praseodymium, dysprosium, samarium, yttrium, gadolinium,erbium, ytterbium, holmium, terbium, europium, thulium, lutetium, andmixtures thereof; and wherein X is chloride, bromide, or iodide.
 15. Theprocess of claim 14 wherein X is chloride, and M is lanthanum or amixture of lanthanum with other rare earth elements.
 16. The process ofclaim 1 wherein the rare earth oxyhalide has a BET surface area greaterthan about 12 m²/g.
 17. The process of claim 1 wherein the rare earthoxyhalide is represented by the formula MOX, wherein M is at least onerare earth selected from the group consisting of lanthanum, cerium,neodymium, praseodymium, dysprosium, samarium, yttrium, gadolinium,erbium, ytterbium, holmium, terbium, europium, thulium, lutetium, andmixtures thereof; and wherein X is chloride, bromide, or iodide.
 18. Theprocess of claim 17 wherein X is chloride, and M is lanthanum or amixture of lanthanum with other rare earth elements.
 19. The process ofclaim 1 wherein the catalyst is bonded to or extruded with a support.20. The process of claim 1 wherein the process is conducted at atemperature greater than about 100° C. and less than about 600° C. 21.The process of claim 1 wherein the process is conducted at a pressureequal to or greater than about 14 psia (97 kPa) and less than about 150psia (1,034 kPa).
 22. The process of claim 1 wherein the process isconducted at a weight hourly space velocity of total feed, comprisingthe reactant alkane, the source of halogen, the optional source ofoxygen, and an optional diluent, of greater than about 0.1 h⁻¹ and lessthan about 1,000 h⁻¹.
 23. The process of claim 1 wherein the halogenatedhydrocarbon product is recycled to the process for conversion intoolefinic product.
 24. The process of claim 1 wherein the olefin isrecycled to the process for conversion into halogenated hydrocarbonproduct.
 25. A process of preparing allyl chloride and propylenecomprising contacting propane with a source of chlorine and a source ofoxygen in the presence of a catalyst at a temperature greater than about150° C. and less than about 500° C. such that allyl chloride andco-product propylene are formed, the catalyst comprising a rare earthhalide or rare earth oxyhalide compound substantially free of iron andcopper such that the atom ratio of rare earth element to iron or copperis greater than about 50/1, with the proviso that when cerium is presentin the catalyst, then at least one rare earth element is also present inthe catalyst.
 26. The process of claim 25 wherein the catalyst is a rareearth chloride or rare earth oxychloride.
 27. The process of claim 25wherein the rare earth is lanthanum.
 28. The process of claim 25 whereinthe co-product propylene is recycled to the process to maximize theproduction of allyl chloride.
 29. The process of claim 25 wherein allylchloride product is recycled to the reactor to maximize the productionof propylene.